Method for producing a nut, screw tap for the performance of the method, and a nut produced according to the method

ABSTRACT

A method of producing a nut having a drive area and a clamping area, and a screw tap for performing the method. A bore hole running through the clamping and drive areas is produced in a cylindrical manner. The screw tap is screwed into the cylindrical bore until a predetermined position is reached. The screw tap is successively provided, when seen in an axial direction from the front side thereof, with a centering/cutting section, an adjoining cutting section which is used to produce a conical internal screw thread section in the clamping area, and a cutting section which is used to produce a cylindrical internal screw thread section in the drive area.

This is a nationalization of PCT/DE01/02287, filed Jun. 20, 2001 andpublished in Germany.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention at hand relates to a method and a screw tap for producinga nut having a drive area and a clamping area which are produced as onepiece, the nut having a bore that is fully engaged in the clamping anddrive areas, with an at least partially cylindrical threaded section inthe drive area and an at least partially conical threaded section in theclamping area. The invention also relates to a nut produced according tothe method.

2. Description of the Related Art

A nut produced by means of massive reshaping is known from DE 195 32709, which has a drive area for the contact of a tool, an area forattaching on a component, as well as a clamping area that is slotted inlongitudinal direction of the nut so that clamping tongues are arrangedbetween two slots each in the circumference direction. Both the clampingarea with the slots and clamping tongues, as well as the drive area areproduced by means of massive reshaping, such as cold and/or hotextrusion. The nut's internal thread extends along the drive area at adiameter that is constant, and that is reduced at increasing distancesfrom the drive area at least across part of the axial extension of theclamping area.

The thread of such a nut is usually produced on NC thread cutters,whereby the bore is initially bored cylindrically in the drive area, andconically in the clamping area, and the thread is then cut on the NCcutter. It is clear that such a production method is complicated andexpensive. In both processes, the tool movement must occur in conformityof this taper.

SUMMARY OF THE INVENTION

The task of the invention at hand therefore consist of the fact ofimproving such a method in such a way that it can be performed in asubstantially simpler manner, and that nuts can be produced a lot moreinexpensively according to this method. Furthermore, a screw tap is tobe created for the performance of this method.

The task named above is solved by means of a method for producing a nutthat has a drive area and a clamping area which are produced as onepiece. The nut has a bore that is fully engaged in the clamping anddrive areas with an at least partially cylindrical internal threadedsection in the drive area, and an at least partially conical internalthreaded section in the clamping area. According to the method and tothe screw tap for performing the method, the bore that is fully engagedin the clamping area and in the drive area is produced as a cylindricalbore, with the screw tap being screwed into the cylindrical bore up to apredetermined position. The screw tap has, in the axial direction viewedfrom its front side, a centering cutting section and a subsequentlyjoining first cutting section that are arranged next to each other forthe production of the conical internal threaded section of the clampingarea, with a subsequently joining second cutting section for theproduction of the cylindrical internal threaded section in the drivearea. The second cutting section has teeth which extend in alongitudinal direction, the first cutting section has teeth that extendat a first angle laterally to the longitudinal direction, and thecentering cutting section has teeth that extend at a second anglelaterally to the longitudinal direction and along a line tapering towardsaid front side, whereby the screw tap is screwed into the bore up tothe predetermined position in a first step. The teeth of the secondcutting section are mapped in the drive area for the production of thecylindrical internal threaded section, and the teeth of the firstcutting section, which extend along an additional line tapering towardsaid front side, are mapped in the drive area or in the clamping area,respectively, for the production of the conical internal threadedsection of the clamping area, whereby the screw tap is turned back fromthe bore of the nut in a subsequent step.

The nut produced according to the method of the present inventioncontains a clamping area, a drive area that is connected to the clampingarea in one piece, and a support area that is arranged on the side ofthe drive area that is opposite of the clamping area. A cylindricalinternal threaded section extends at least partially across the drivearea in a bore that is in the area of the drive area, and a conicalinternal threaded section is arranged that extends at least partiallyacross the clamping area in the clamping area; these threaded sectionsare produced in one step by screwing in a screw tap into the cylindricalbore up to a predetermined position, as has just been summarized above.The clamping area is embodied in the shape of a core, and is limited inits external circumference by a conical, or tapered extending lateralarea, the tip of which faces the opposite direction of the support area.The clamping area has several axially positioned recesses that aredistributed across the circumference, which axially extend at least upto the drive area. The drive area may further include deformations atregular intervals on the radial exterior, on which a tool can be placedfor turning out of the nut on a bolt.

The substantial advantage of the invention at hand consists of the factthat the complicated steps for conically boring the clamping area, andfor inserting an internal thread by means of an NC machine that arerequired in relation to prior art can be omitted, because a specialscrew tap for the production of the internal thread is used, which isalready conically formed, and is inserted into a bore that iscylindrical in the area of the clamping area and of the drive area. Morespecifically, the screw tap used in relation to the method according tothe invention is embodied in such a way that in addition to acylindrical thread cutting section for the production of the cylindricalinternal thread, it has a special conical thread cutting section in thedrive area for the production of the conical area of the internal threadin the clamping area by means of simple screwing in of the screw tap upto a predetermined axial position. It is of particular importance thatthe screw tap performs merely a simple, straightforward movement.

According to a further advantageous embodiment of the method, when thescrew tap has been screwed into the bore up to the predeterminedposition, the teeth of the second cutting section are arranged in anentirety of the drive area for the production of the cylindricalinternal threaded section, and the teeth of the first cutting sectionare arranged in an entirety of the clamping area for the production ofthe conical internal threaded section.

As another embodiment, when the screw tap has been screwed into the boreup to the predetermined position, the teeth of the second cuttingsection are arranged in the drive area and also are partially engaged inthe clamping area for the production of the cylindrical internalthreaded section.

As a further embodiment, when the screw tap has been screwed into thebore up to the predetermined position, the teeth of the first cuttingsection for the production of the conical internal threaded section ofthe clamping area also at least partially engage into the drive area.

According to further advantageous embodiments of the screw tap, theteeth of the second cutting section may have circular heads and circularlegs in the longitudinal direction of the screw tap for the productionof the cylindrical internal threaded section of the drive area. Theteeth of the first cutting section may also have circular heads that arepositioned on a lateral area that is tilted at a first angle to thelongitudinal direction of the screw tap, and a tooth height of the teethof the first cutting section may increase in size toward the front sideof the screw tap.

As additional embodiments, the teeth of the first cutting section mayhave circular legs that are arranged on a lateral area that is tilted atthe first angle in relation to the longitudinal direction of the screwtap. The teeth of the centering cutting section may have circular headsthat are positioned on a lateral area that is tilted at a second angleto the longitudinal direction of the screw tap, with the second anglepreferably being larger than the first angle and with the teeth of thecentering cutting section having a tooth height that decreases towardthe front side.

Further, the teeth of the centering cutting section may have circularlegs that are positioned on a lateral area that is tilted at a thirdangle in relation to the longitudinal direction of the screw tap, withthe third angle corresponding to the first angle.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention and its embodiments are further explained in detail inrelation to the figures. They show:

FIG. 1 a longitudinal section across a nut produced in accordance to theinventive method;

FIG. 2 a view onto the nut of FIG. 1 from the side opposite of the base;

FIG. 3 the side view of the inventive screw tap used in relation to themethod according to the invention;

FIG. 4 a section across the screw tap of FIG. 3 along the line VI—VI;

FIG. 5 an enlarged illustration of the various, and

FIG. 6 of the screw tap screwed into a nut up to a predeterminedposition.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Further scope of applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

The nut illustrated in FIG. 1 essentially consists of a drive area 2 anda clamping area 3, which are both produced as one piece. On the sidefacing the base, i.e., on the side opposite of the clamping area 3, thenut has a support area 5. The cylindrical threaded section of the drivearea 2 of the nut is identified by 7.

The drive area 2 has deformations 9 at regular intervals on its radialexterior, which, for instance, form a multitude of edges, and areprovided for the contact of the tool, with the aid of which the nut canbe pivoted on a bolt, or similar.

The clamping area 3 that axially joins the drive area 2 is embodied as acore, and is limited in its outer circumference by a conically, or tapershaped lateral area 9, the cone tip of which faces in the oppositedirection of the support area 5. The clamping area 3 has several slots,or axially directed recesses 11 that are distributed across thecircumference, which axially extend up to the drive area 2. The clampingtongues formed between two slots each are identified by 13. The conicalthreaded section of the clamping area 3 is identified by 8.

It has already been pointed out that normally the threaded sections 7and 8 are produced by initially inserting a cylindrical bore into thedrive area 2, and a conical bore into the clamping area 3, and that thecylindrical threaded section 7, and the conical threaded section 8 aresubsequently produced with the aid of an NC thread cutter.

According to the method at hand, the threaded sections 7 and 8 areproduced by means of manufacturing only one single axially extendingcylindrical bore B in that a screw tap 15 embodied according to FIG. 3is screwed into the cylindrical bore B from the side of the support area5 up to a predetermined position in a manner to be further explained asfollows. The bore can preferably be produced by reshaping.

The screw tap 15 has three different threaded cutting sections that arearranged next to each other, viewed in axial direction from the front.The front most centering cutting section 17 is first inserted into thecylindrical bore of the nut and serves for the purpose of centering thescrew tap 15 in relation to the cylindrical bore B of the nut, and topre-cut the thread in the section 21. The cutting section 19 joins thecentering cutting section 17, which serves for the production of theconical internal thread of the clamping area 3. In addition to thecutting section 19, a third cutting section 21 is positioned on the sideopposite of the centering cutting section 17, which serves the purposeof producing the cylindrical internal threaded section 7 in the drivearea 2 of the nut.

The previously mentioned cutting sections 17, 19, and 21 are illustratedgrossly enlarged in FIG. 5. Accordingly, the cutting section 21 providedfor the production of the cylindrical internal threaded section 7 in thedrive area 2 has teeth, the circular heads 23 and circular legs 25 ofwhich extend in longitudinal direction L.

The teeth of the cutting section 19 are identified by 26. They areembodied in such a way that their circular heads 27 each are positionedon an intended lateral area, which is tilted at an angle α1 to thelongitudinal direction L so that the teeth 26 each have a smaller toothheight toward the front side of the screw tap 15. Preferably, thecircular legs 29 of the teeth 26 of the cutting section 19 are alsoarranged at an angle αl in relation to the lateral area that is tiltedtoward the axial direction L.

Finally, the teeth 30 of the centering cutting section 17 are created insuch a way that their circular heads 31 are positioned on an intendedlateral area that is tilted toward the longitudinal axis of the screwtap 15 at an angle α2, whereby the angle α2 preferably is larger thanthe angle α1. Preferably, the teeth 30 have a teeth height thatdecreases toward the direction of the front side. Preferably, therespective circular legs 33 of the teeth 30 are also arranged on anintended lateral area at an angle in relation to the longitudinal axisL, which, for instance, corresponds to angle α1.

According to the inventive method, the screw tap 15 is screwed intocontinuous, i.e., both in the clamping area 3, and in the drive area 2cylindrically extending bore of a nut that is centered and clamped inthe thread cutter up to an axial position until the cutting section 19is located at the desired position of the clamping area 3, and thecutting section 21 is at the desired position at the drive area 2. Thecutting section 17 protrudes at least partially across the clamping area3 of the nut. After the mentioned predetermined position has beenachieved, the desired conical thread is therefore created in theclamping area 3, and the teeth 22 of the cutting section 21 are mappedexactly in the drive area 2. This condition is illustrated in FIG. 6.Finally, the screw tap 15 is turned back from the predeterminedposition, and is removed from the nut. The teeth 30 and/or 26 of thecutting sections 17 and 19 serve for precutting of the teeth of theinternal thread 7 of the drive area during the screwing in of the screwtap 15 up to the predetermined position. Accordingly, the teeth 30 ofthe section 17 serve for precutting of the teeth of the internal thread8 of the clamping area.

It must be pointed out that the cutting sections 19 and 21 can bedimensioned in such a way that part of the teeth 22 of the cuttingsection 21 can also be penetrated into the clamping area 3 in thepredetermined position so that the created cylindrical threaded section7 extends beyond the drive area 2, partially into the clamping area 3.In reverse order it is also possible to dimension the cutting sections19 and 21 in such a way that part of the teeth 26 of the cutting section19 also penetrate the drive area 2 in the predetermined position.

It must be further pointed out that the term “conical” means all shapesthat taper toward the front side of the screw tap 15.

The invention being thus described, it will be apparent that the samemay be varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be recognized by one skilled in the art areintended to be included within the scope of the following claims.

1. A method for producing a nut that has a drive area and a clampingarea which are produced as one piece, the nut having a bore that isfully engaged in the clamping area and the drive area with an at leastpartially cylindrical internal threaded section in the drive area, andan at least partially conical internal threaded section in the clampingarea, comprising the steps of: producing the bore that is fully engagedin the clamping area and in the drive area as a cylindrical bore;screwing a screw tap into said cylindrical bore up to a predeterminedposition, said screw tap having in axial direction, viewed from a frontside thereof, a centering cutting section and a subsequently joiningfirst cutting section that are arranged next to each other for theproduction of the conical internal threaded section of the clampingarea, and a subsequently joining second cutting section for theproduction of the cylindrical internal threaded section in the drivearea, said second cutting section having teeth which extend in alongitudinal direction, said first cutting section having teeth thatextend at a first angle laterally to the longitudinal direction, and thecentering cutting section having teeth that extend at a second anglelaterally to said longitudinal direction; mapping said teeth of thesecond cutting section in the drive area of the nut for the productionof the cylindrical internal threaded section, and mapping the teeth ofthe first cutting section in the drive area, or in the clamping area,respectively, of the nut for the production of the conical internalthreaded section of the clamping area; and subsequently turning back thescrew tap from the bore of the nut.
 2. The method according to claim 1,wherein in said predetermined position, the teeth of the second cuttingsection are arranged in an entirety of the drive area for the productionof the cylindrical internal threaded section, and the teeth of the firstcutting section are arranged in an entirety of the clamping area for theproduction of the conical internal threaded section.
 3. The methodaccording to claim 1, wherein in the predetermined position, the teethof the second cutting section are arranged in the drive area and alsoare partially engaged in the clamping area for the production of thecylindrical internal threaded section.
 4. The method according to claim1, wherein in the predetermined position, the teeth of the first cuttingsection for the production of the conical internal threaded section ofthe clamping area also at least partially engage into the drive area. 5.A screw tap for producing a nut that has a drive area and a clampingarea which are produced as one piece, the nut having a bore that isfully engaged in the clamping area and the drive area with an at leastpartially internal cylindrical threaded section in the drive area, andan at least partially conical internal threaded section in the clampingarea, said screw tap producing said bore as a cylindrical bore and beingscrewed therein up to a predetermined position, said screw tapcomprising: a centering cutting section at a front side of said screwtap and a subsequently joining first cutting section adjacent thereto inan axial direction for the production of the conical internal threadedsection of the clamping area; a subsequently joining second cuttingsection adjacent said first cutting section in the axial direction forthe production of the cylindrical internal threaded section in the drivearea; said second cutting section having teeth that extend in alongitudinal direction, said first cutting section having teeth thatextend along a line tapering toward said front side, and said centeringcutting section having teeth that extend along an additional line thattapers toward said front side.
 6. The screw tap according to claim 5,wherein the teeth of the second cutting section have circular heads andcircular legs in the longitudinal direction of the screw tap for theproduction of the cylindrical internal threaded section of the drivearea.
 7. The screw tap according to claim 5, wherein the teeth of thefirst cutting section have circular heads that are positioned on alateral area that is tilted at a first angle to the longitudinaldirection of the screw tap.
 8. The screw tap according to claim 7,wherein a tooth height of the teeth of the first cutting sectionincreases in size toward the front side of the screw tap.
 9. The screwtap according to claim 7, wherein the teeth of the first cutting sectionhave circular legs that are arranged on a lateral area that is tilted atsaid first angle in relation to the longitudinal direction of the screwtap.
 10. The screw tap according to claim 7, wherein the teeth of thecentering cutting section have circular heads that are positioned on alateral area that is tilted at a second angle to the longitudinaldirection of the screw tap.
 11. The screw tap according to claim 10,wherein the second angle is larger than the first angle.
 12. The screwtap according to claim 10, wherein the teeth of the centering cuttingsection have a tooth height that decreases toward the front side. 13.The screw tap according to claim 10, wherein the teeth of the centeringcutting section have circular legs that are positioned on a lateral areathat is tilted at a third angle in relation to the longitudinaldirection of the screw tap.
 14. The screw tap according to claim 13,wherein the third angle corresponds to the first angle.